Studies on photochemical rearrangement of non-oxygenated bicyclo[2.2.2]octenones and mono-oxygenated bicyclo[2.2.2]octenones from masked o-benzoquinones: Access to protoilludane and marasmane skeletons

Article abstract of DOI:10.1002/jccs.201900460

In this work, we described flexible approaches to protoilludane-like (5,6,4-tricyclic ring) and marasmane-like (5,6,3-tricyclic ring) skeletons with naturally occurring cis/anti/cis stereochemistry using photochemical rearrangement of bicyclo[2.2.2]octeno

Full text of DOI:10.1002/jccs.201900460

Received: 29 October 2019
DOI: 10.1002/jccs.201900460
Revised: 19 December 2019
Accepted: 27 December 2019
S P E C I A L I S S U E P A P E R
Studies on photochemical rearrangement of non-
oxygenated bicyclo[2.2.2]octenones and mono-oxygenated
bicyclo[2.2.2]octenones from masked o-benzoquinones:
Access to protoilludane and marasmane skeletons
Wei-Chun Hung | Yung-Ching Chen | Guang-Hao Niu | Gary J. Chuang
Department of Chemistry, Chung Yuan
Abstract
Christian University, Chungli, Taiwan,
Republic of China
In this work, we described flexible approaches to protoilludane-like (5,6,4-tricyclic
ring) and marasmane-like (5,6,3-tricyclic ring) skeletons with naturally occurring
cis/anti/cis stereochemistry using photochemical rearrangement of bicyclo[2.2.2]
octenones and Diels-Alder reaction of masked o-benzoquinones as the key steps.
Correspondence
Gary J. Chuang, Department of
Chemistry, Chung Yuan Christian
University, 200 Chung Pei Road, Chungli
District, Taoyuan City 32023, Taiwan,
Republic of China.
K E Y W O R D S
bicyclo[2.2.2]octenones, marasmane, masked o-benzoquinones, photoreaction, protoilludane
Email: gjchuang@cycu.edu.tw
Funding information
Ministry of Science and Technology,
Taiwan, Grant/Award Number: MOST-
108-2113-M-033-007
1 | INTRODUCTION
protoilludane.[7]8c In addition, some cases were reported
that products of PIDM resulted from 1,3-acyl migration
Bicyclo[2.2.2]octenone housing β,γ-unsaturated carbonyl
chromophore has shown significant reactivity in
photochemistry,[1] and therefore the photochemical
rearrangement of bicyclo[2.2.2]octenone has proven to be
an useful tool for forging of carbon skeleton in total syn-
thesis of natural products or complex molecular frame-
works.[2] For instance, the use of oxa-di-π-methane
rearrangement in total synthesis of ( )-magellanine[3]
and the formal synthesis of ( )-pentalenolactone A
methyl ester.[4] Additionally, utilization of photoinduced
1,3-migration could also be found in the enantiomeric
synthesis of (+)-armillarivin[5] and formal synthesis of
( )-coriolin.[6] Another type of photochemically mediate
reaction, which involved 1,3-acyl migration and addi-
tional decarbonylation, we called it photoinduced
decarbonylative 1,3-migration (PIDM), can be used in
construction of some natural occurring skeletons, like
via prolonged irradiation with ultraviolet (UV) light.[8]
Recently, we have enticed to the unique tricyclic
5,6,3-framework (marasmane skeleton),[7] which consists
in a number of bioactive sesquiterpenoids such as
isovelleral[9] and its derivitives[10] (Figure 1). Although
many of promising synthetic strategies for the angularly
tricyclic structure and approaches to isovelleral have been
demonstrated;[9] an efficient route toward the marasmane
core still has presented many synthetic challenges.
Previous synthetic efforts in our laboratory were
targeted at the tricyclic 5,6,3-framework, and we have
reported a rapid approach to which via PIDM.[11] On the
basis of our recent experiences, the efficient decarbonylative
rearrangement of 6a results from the formation of relatively
stable dimethyl ketal radical species biradical II
(Scheme 1) to yield the PIDM product. Based on this knowl-
edge, we became interested in how the existence of oxygen
© 2020 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2020;1–16.
http://www.jccs.wiley-vch.de
1

2
HUNG ET AL.
FIGURE 1 Bioactive sesquiterpenoids containing marasmane
skeleton
SCHEME 2 Photoreactions of bicyclo[2.2.2]octenones
2.2 | Photoinduced reaction of
demethoxylated bicyclo[2.2.2]octenones
SCHEME 1 Proposed reaction pathway for photoinduced
decarbonylative 1,3-migration of 6a
Having the various bicyclo[2.2.2]octenones in hand, we
then carried out the photoinduced reaction of
demethoxylated bicyclo[2.2.2]octenones. As shown in
Table 2, the selected D-A adducts 6a, 6b, and 7a under-
went reductive deketalization with SmI2 at room tempera-
ture to give 8a, 8b, and 9a in 24–88% yield, which were
subsequently examined the photoinduced rearrangement.
Unfortunately, after 1.5 hr irradiation with a broad band
UV light centered at 306 nm, deketal product 8a was
transformed to the 1,3-acyl migration product 10a in 42%
isolated yield instead of the desired PIDM product 12a
(Table 2, entry 1). The same results were obtained in the
examples of 8b and 9a, which gave the corresponding
1,3-acyl migration product 10b, 11a in 53 and 16% yield,
respectively (Table 2, entries 2–3). The structures of photo-
adjacent to carbonyl group on bicycle ring affects reaction
pathway during irradiation of UV light. Herein, we report
the photoreaction of nonoxygenated bicyclo[2.2.2]octenones
and mono-oxygenated bicyclo[2.2.2]octenones (Scheme 2).
2 | RESULTS AND DISCUSSION
2.1 | Synthesis of various bicyclo[2.2.2]
octenones for the photoinduced reaction
To prepare bicyclo[2.2.2]octenones as the starting material
for photoinduced reactions, we applied the Diels-Alder reac-
tion of masked o-benzoquinone (MOB), which were devel-
oped by Liao and Quideau.[12] The preparation of bicyclo
[2.2.2]octenones were depicted in Table 1. MOBs 2 were rap-
idly generated in situ from 2-methoxyphenols 1 in the pres-
ence of (diacetoxy)iodobenzene (PhI(OAc)2), and directly
underwent efficient self-Diels-Alder reaction to afford dimer
3 in refluxing methanol.[13,14] Subsequent reaction of the
resulting dimer with the selected dienophile 4 (for its high
reactivity) and 5 (for its structure that resemble the five-
member ring on marasmane skeleton) provided the
corresponding cycloaddition products 6 and 7 in 66–92%
yield, respectively via a retro Diel-Alder/Diels-Alder process.
1
reaction were established by H, 13C, DEPT NMR, and
HRMS. It is not surprising to afford the protoilludane-like
results, which probably proved that bicyclo[2.2.2]
octenones bore dimethyl ketal adjacent to carbonyl group,
which was required to stabilize the radical intermediate
and promote 1,3-acyl migration instead of PIDM.8c
2.3 | Photoinduced reaction of
α-hydroxybicyclo[2.2.2]octenones
Our next object was to examine the photoreaction of
α-hydroxybicyclo[2.2.2]octenones, which could be synthesized

HUNG ET AL.
3
TABLE 1 Preparation of bicyclo[2.2.2]octenones 6 and 7 from 2-methoxyphenols 1
Entry
1
2-Methoxyphenol
Diel-Alder adduct
Yielda (%) Entry
2-Methoxyphenol
Diel-Alder adduct
Yielda (%)
85
92
4
2
3
87
5
83
66
73
6
[a] The yields of two steps were determined after column chromatography.
from D-A products 7. In the two-step sequence, D-A products
7 were first treated with NaBH4 for carbonyl group reduction
to deliver the exo isomer and the endo isomer, and then the
obtained epimeric ketal alcohols were hydrolyzed under
acidic conditions to afford 13 in 19–34% yields and 14 in
21–68% yields (Table 3). To expand the tolerance of functional
groups, 7d (for its ketal group that resemble aldehyde moiety
on natural product, isovelleral; Figure 1) was elaborated to
α-hydroxybicyclo[2.2.2]octenone isomers 13d and 14d in
four-step sequence (Scheme 3). Exposure of 7d to HCl in ethyl
acetate and water at room temperature, followed by Wittig
olefination of the resulting aldehyde 15, delivered vinylated
product 16 in 62% isolated yield. Subsequently, a two-step
reduction/hydrolysis protocol was used to give a pair of iso-
mers, 13d and 14d, in 36 and 31% isolated yields, respectively.
The stereochemistry of 13a, 14a was diagnosed with nuclear
overhauser effect (NOE) experiments. In addition, 14a pro-
vided single crystals, which allowed to be further confirmed
by X-ray analysis (Figure 2).
no desired product detected in 1H NMR of the crude prod-
uct mixture. Despite the reaction, solvent was switched
from acetonitrile to benzene, none of which were success-
ful. Considering that the free hydroxyl group on 13 or 14
would frustrate the photoreaction, we planned to apply
tert-butyldimethylsilyl (TBS) protection of 13 and 14 before
irradiation of UV light. The results of cases of PIDM prod-
ucts 17 and 18 were successfully obtained and are shown
in Table 4. The exo isomer 13a proceeded silyl protection/
photolysis sequence to provide the antiproduct 18a (the
relative orientation between -OTBS and bridgehead hydro-
gen atom on cyclopropane ring) in 57% yield, and syn
product 17a was isolated from endo isomer 14a in 52%
yield (Table 4, entries 1–2). Of note, apart from non-
substituent cases, substituents at C-8 or C-10 led to unex-
pected epimerization at C-9 during photolysis. The exo
isomers 13b-d were found to form the syn products 18b-d
(29–65% yield) as the major products along with minor
antiproducts 17b-d (7–11% yield) (Table 4, entries 3, 5 and
7), in contrast, the endo isomers 14b-d underwent PIDM
reaction to give the major antiproduct 17b-d (32–58%
yield), accompanied by minor syn product 18b-d (10–28%
yield) (Table 4, entries 4, 6 and 8).
With the synthesized α-hydroxybicyclo[2.2.2]octenones
13 and 14 in hand, we then examined photoinduced reac-
tions of selected 13a and 14a. Under photolysis conditions,
both 13a and 14a unfortunately gave complex mixture with

4
HUNG ET AL.
TABLE 2 Photoinduced reaction of demethoxylated bicyclo[2.2.2]octenones
Entry
1
Diel-Alder adduct
Deketal product
Yielda (%)
62b
Product 10, 11
Yielda (%)
42
2
3
88b
53
16
24c
[a] Isolated yield. [b] Reaction time: 0.5 h. [c] Reaction time: 6 h.
TABLE 3 Preparation of α-hydroxybicyclo[2.2.2]octenones from Diels-Alder products of MOBs
Entry
1
Diel-Alder adduct
Product 13+14
Yielda (%)
13a (19)+14a (68)
13b (34)+14b (21)
13c (34)+14c (32)
2
3
[a] The yields of two steps were determined after column chromatography.
The unexpected epimerization during the photolysis
of 13b was proposed in two plausible pathways. Path A
involves that biradical III was generated from 19b
through Norrish type I cleavage, immediately releasing
CO to form biradical IV. Finally, PIDM products 17b
and 18b were given by recombination of biradical IV

HUNG ET AL.
5
useful tool for building strained and complex molecular
frameworks.
4 | EXPERIMENTAL
4.1 | General information
Reactions were carried out under ambient atmosphere
unless otherwise specified. Methanol and dichloromethane
were dried by distillation from CaH2. tetrahydrofuran
(THF) was dried by distillation from Na/benzophenone.
Commercially obtained reagents were used as received
unless otherwise specified. Tributyltin hydride was pur-
chased from Merck, Acros, and Alfa Aesar. Photoreaction
was carried out using PANCHUM Photochemical Reactor
PR-2000. Yields refer to purified and spectroscopically pure
compounds. Thin-layer chromatography (TLC) was per-
formed using Merck TLC Aluminum sheets silica gel
60 F254 plates and visualized by fluorescence quenching
under UV light and KMnO4 stain. Flash chromatography
was performed using silica gel (Chromatorex, MB
70-40/75, 40–75 μm) purchased by Fuji Silysia Chemicals.
NMR spectra were recorded on a Bruker AVANCE spec-
trometer operating at 300 MHz for 1H and 75 MHz for 13C,
Bruker AVANCE II operating at 400 MHz for 1H and
100 MHz for 13C acquisitions, respectively. Chemical shifts
are reported in ppm with the solvent resonance as the
internal standard: CDCl3 = 7.26 (1H), 77.0 (13C). Data are
reported as follows: s = singlet, br = broad, d = doublet,
t = triplet, q = quartet, m = multiplet; coupling constants
in Hz; integration. High-resolution mass spectra were
obtained on JMS-700 at the Academia Sinica.
SCHEME 3 Synthesis of α-hydroxybicyclo[2.2.2]octenones
13d and 14d
The analytical data for compounds 6a-b, 7a-d are
identical with those already reported in the literature.[11]
FIGURE 2 NOE experiments of 13a, 14a and ORTEP diagram
of 14a
(Scheme 4, path A). Alternative pathway involves the
combination of biradical III afforded 5,6,4-tricyclic com-
pound 11b, followed by the second time Norrish type I
cleavage and sequential extrusion of CO to provide PIDM
products 17b and 18b (Scheme 4, path B).
4.2 | General procedure for
deketalization of bicyclo[2.2.2]octenones
(synthesis of 8a as example)
Preparation of SmI2/THF solution (Kagan's method): An
oven-dried 100 ml round-bottomed flask equipped with a
Teflon-coated magnetic stir bar and a septum was placed
under a positive pressure of argon. In air, samarium metal
(11.48 g, 76.4 mmol) and 1,2-diiodoethane (10.77 g,
38.2 mmol) were weighed out and added to the reaction
flask. The flask was sealed with a septum, and stirring was
started at medium speed. Freshly dried THF (220 ml) was
added at 0ꢀC and the septum was sealed with Parafilm. After
being stirred for 30 min, the ice bath was removed and the
mixture was stirred at room temperature overnight. The
deep blue solution was allowed to use for the deketalizaiton.
3 | CONCLUSIONS
In summary, we present versatile methods to achieve
functionalized protoilludane-like skeleton via 1,3-acyl
migration of nonoxygenated bicyclo[2.2.2]octenones, and
marasmane-like skeleton by PIDM of mono-oxygenated
bicyclo[2.2.2]octenones, which could be easily obtained
by the Diels-Alder reaction of mask o-benzoquinones. We
anticipate these successful transformations will be a

6
HUNG ET AL.
TABLE 4 TBS protection/photoinduced decarbonylative 1,3-acyl migration of 13 and 14
Entry Precursor 13 or 14
PIDM product 17+18
Yielda (%)
1b
18a (57)
2b
17a (52)
3
17b (7)+18b (55)
4
5
17b (37)+18b (10)
17c (7)+18c (65)
6
17c (32)+18c (19)
7
8
17d (11)+18d (29)
17d (58)+18d (28)
[a] The yields of two steps were determined after column chromatography.
[b] Irradiation of UV light for 17 h.
To a stirred solution of 6a (0.327 g, 1.00 mmol) in the
mix solvent of dry THF (1 ml) and dry MeOH (0.4 ml,
d = 0.791 g/ml) was added to the freshly prepared SmI2/
THF solution in a dropwise manner at room temperature
(Caution: SmI2 solution was extremely air sensitive,
make sure to run this reaction under inert gas). After
being stirred for a period of time (Table 2 for the duration
of reaction time), the reaction mixture was opened to air
until the blue color was faded. The reaction mixture was
filtered through a pad of Celite® then concentrated under
reduced pressure to remove THF. The residue was
diluted with CH2Cl2, and the organic layer was washed
sequentially with 1 N HCl, saturated aqueous Na2S2O3,
and brine. The organic solution was dried over MgSO4,

HUNG ET AL.
7
SCHEME 4 Proposed mechanism
for the generation of 17b and 18b
from 19b
filtered, and concentrated. The residue was purified by
flash chromatography on silica gel (EtOAc: n-Hex-
ane = 1:10 ! 1:3) to afford 8a (0.166 g, 62% yield) as a
white solid.
575, 539, 513; HRMS (APCI) m/z calcd for C17H15NO3
[M + H]+ 282.1130, found 282.1132.
4.5 | (3aR*,4R*,7S*,7aR*)-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-9-one (9a)
4.3 | (3aR*,4S*,7R*,7aS*)-2-phenyl-
3a,4,7,7a-tetrahydro-1H-4,7-ethanoisoindole-
1,3,8(2H)-trione (8a)
White solid, 40 mg, 25% yield, Rf = 0.35 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.38–6.27 (m, 1H), 6.03–6.01 (m, 1H), 5.64 (dd,
J = 6.3, 2.3 Hz, 1H), 5.42 (dd, J = 4.8, 2.3 Hz, 1H),
3.23–3.09 (m, 2H), 3.02–2.96 (m, 1H), 2.73–2.62 (m, 1H),
2.59–2.48 (m, 1H), 2.05 (d, J = 2.8 Hz, 2H), 2.02–1.85 (m,
White solid, 166 mg, 62% yield; Rf = 0.25 (silica gel,
EtOAc: n-Hexane = 1:3); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 7.51–7.37 (m, 3H), 7.23–7.16 (m, 2H), 6.56 (ddd,
J = 7.8, 6.2, 1.3 Hz, 1H), 6.32 (ddd, J = 8.1, 6.2, 1.8 Hz,
1H), 3.79 (ddd, J = 6.4, 3.1, 1.3 Hz, 1H), 3.71–3.66 (m,
1H), 3.40–3.26 (m, 2H), 2.23 (ddd, J = 2.9 Hz, 2H); 13C
NMR (75 MHz, CDCl3, 24ꢀC, δ) 206.9 (C), 176.1 (CH),
175.1 (CH), 135.3 (CH), 131.5 (CH), 129.2 (2xCH), 128.9
(CH), 127.6 (CH), 126.3 (2xCH), 49.5 (CH), 44.0 (CH),
41.0 (CH), 38.1 (CH2), 34.5 (CH); IR (neat, cm−1) 1,732,
1,700, 1,592, 1,496, 1,455, 1,382, 1,224, 1,185, 1,096, 1,059,
955, 876, 830, 797, 763, 744, 721, 692, 621, 502; HRMS
(EI) m/z calcd for C16H13NO3 [M]+ 267.0895, found
267.0893.
13
1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 212.8 (C), 134.4
(CH), 132.7 (CH), 130.2 (CH), 128.3 (CH), 52.7 (CH), 49.5
(CH), 40.3 (CH2), 39.9 (CH), 38.9 (CH2), 37.6 (CH); IR
(neat, cm−1) 1,718, 1,442, 987, 936, 894, 869, 744, 675,
540; HRMS (ESI) m/z calcd for C11H12O [M]+ 160.0888,
found 160.0885.
4.6 | General procedure of the
photoreaction of demethoxylated
compound 8 or 9 (synthesis of 10a as
example)
4.4 | (3aR*,4S*,7R*,7aR*)-7-methyl-
2-phenyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoisoindole-1,3,8(2H)-trione (8b)
To a solution of 8a (70 mg, 0.262 mmol) in acetonitrile
(70 ml) was transferred into the quartz tube and degassed
by purging with N2 for 45 min. The reaction mixture was
irradiated with a broad band centered at 306 nm in a
Rayonet-type photoreactor and stirred for 90 min. The
reaction mixture was then concentrated under reduced
pressure. The residue was purified by flash chromatogra-
phy on silica gel (EtOAc: n-Hexane = 1:50 ! 1:20) to
afford 10a (30 mg, 42% yield, 57% brsm) as a white solid.
White solid, 221 mg, 88% yield; Rf = 0.28 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 7.44 (ddd, J = 12.5, 7.9, 6.1 Hz, 3H), 7.23–7.17
(m, 2H), 6.56 (ddd, J = 7.8, 6.2, 1.3 Hz, 1H), 6.32 (ddd,
J = 8.1, 6.2, 1.8 Hz, 1H), 3.79 (ddd, J = 6.4, 3.1, 1.3 Hz,
1H), 3.71–3.65 (m, 1H), 3.37 (dd, J = 8.5, 3.0 Hz, 1H),
3.29 (dd, J = 8.4, 3.2 Hz, 1H), 2.23 (t, J = 2.9 Hz, 3H),
13
1.67 (s, 1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 208.5
4.7 | (3aS*,5aS*,7aS*,7bR*)-2-phenyl-
3a,7,7a,7b-tetrahydro-1H-cyclobuta[e]
isoindole-1,3,6(2H,5aH)-trione (10a)
(C), 176.1 (C), 174.6 (C), 162.3 (C), 134.6 (CH), 131.4 (C),
133.3 (CH), 129.2 (2xCH), 128.9 (CH), 126.4 (2xCH), 74.0
(CH3), 45.7 (CH), 45.0 (CH), 38.1 (CH2), 33.9 (CH); IR
(neat, cm−1) 1,701, 1,593, 1,492, 1,455, 1,382, 1,305, 1,229,
1,188, 1,093, 988, 847, 805, 781, 738, 692, 644, 622,
White solid, 30 mg, 42% yield; Rf = 0.34 (silica gel,
1
EtOAc: n-Hexane = 1:20); H NMR (400 MHz, CDCl3,

8
HUNG ET AL.
24ꢀC, δ) 7.53–7.37 (m, 2H), 7.31–7.24 (m, 2H), 6.08 (ddd,
J = 10.1, 3.0, 2.0 Hz, 1H), 5.95 (ddd, J = 10.1, 4.6, 2.4 Hz,
1H), 3.87–3.79 (m, 1H), 3.75–3.70 (m, 1H), 3.56–3.43 (m,
2H), 3.35 (ddd, J = 17.3, 9.0, 4.8 Hz, 1H), 3.17 (ddd,
J = 17.4, 8.9, 2.8 Hz, 1H), 1.27 (s, 1H); 13C NMR (75 MHz,
CDCl3, 24ꢀC, δ) 202.1 (C), 176.4 (C), 174.9 (C), 131.5
(CH), 129.2 (2xCH), 128.7 (CH), 126.2 (2xCH), 123.2
(CH), 122.7 (CH), 57.5 (CH), 50.4 (CH2), 39.9 (CH), 39.1
(CH), 19.7 (CH); IR (neat, cm−1) 2,914, 2,361, 1,776,
1,706, 1,495, 1,374, 1,175, 1,107, 815, 779, 754, 724,
691, 666. HRMS (EI) m/z calcd for C16H13NO3 [M]+
267.0895, found 267.0900.
4.10 | General procedure for NaBH4
reduction/hydrolysis of bicyclo[2.2.2]
octenones 7 (synthesis of 13a and 14a as
example)
To a stirred solution of 7a (0.220 g, 1.00 mmol) in MeOH
(10 ml) was added NaBH4 (0.038 g, 1.0 mmol) at 0ꢀC. The
reaction mixture was warmed to room temperature. After
the consumption of 7, the reaction mixture was quenched
with saturated aqueous NH4Cl solution and extracted
with CH2Cl2 several times. The combined organic layers
were dried over MgSO4, filtered, and concentrated. The
residue was purified by flash chromatography on silica
gel (EtOAc: n-Hexane
=
1:10 ! 1:4) to afford
4.8 | (3aS*,5aS*,7aS*,7bS*)-7a-methyl-
2-phenyl-3a,7,7a,7b-tetrahydro-1H-
cyclobuta[e]isoindole-1,3,6(2H,5aH)-
trione (10b)
unseparated alcohols S1a and S2a (0.222 g, 99% yield) as
a sticky colorless oil. To a stirred solution of the above oil
(0.222 g, 1.00 mmol) in ethyl acetate (5 ml) was sequen-
tially added deionic water (5 ml) and 1 N HCl solution
(3 ml) at room temperature. After being stirred for 3 hr,
the reaction mixture was quenched with saturated aque-
ous NaHCO3 solution and extracted with CH2Cl2 several
times. The combined organic layers were dried over
MgSO4, filtered, and concentrated. The residue was puri-
fied by flash chromatography on silica gel (EtOAc: n-Hex-
ane = 1:10 ! 1:2) to afford two white solid 13a (34 mg,
19% yield) and 14a (122 mg, 69% yield), respectively.
White solid, 37 mg, 53% yield; Rf = 0.30 (silica gel,
1
EtOAc: n-Hexane = 1:20); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 7.52–7.37 (m, 3H), 7.30–7.25 (m, 2H), 5.64
(dd, J = 4.1, 2.1 Hz, 1H), 3.81–3.72 (m, 1H), 3.68–3.40
(m, 3H), 3.36–3.08 (m, 2H), 2.04 (s, 3H); 13C NMR
(75 MHz, CDCl3, 24ꢀC, δ) 202.8 (C), 176.4 (CH), 173.8
(CH), 131.6 (CH), 129.5 (CH), 129.1 (2xCH), 128.6
(CH), 126.2 (2xCH), 118.4 (CH), 58.0 (CH), 50.1 (CH2),
42.7 (CH), 41.7 (CH), 22.1 (CH3), 19.5 (CH); IR (neat,
cm−1) 2,917, 2,360, 2,360, 1,776, 1,708, 1,595, 1,497,
1,455, 1,403, 1,383, 1,319, 1,289, 1,218, 1,175, 1,085,
911, 844, 748, 730, 694, 568, 519, 498, 445; HRMS (ESI)
m/z calcd for C17H15NO3 [M + H]+ 282.1130, found
282.1123.
4.11 | (3aR*,4R*,7S*,7aS*,9R*)-9-hydroxy-
3a,4,7,7a-tetrahydro-1H-4,7-ethanoinden-
8-one (13a)
White solid, 34 mg, 19% yield; Rf = 0.13 (silica gel, EtOAc:
1
n-Hexane = 1:2); H NMR (400 MHz, CDCl3, 24ꢀC, δ)
6.32–6.26 (m, 1H), 6.13–6.08 (m, 1H), 5.72–5.66 (m, 1H),
5.53–5.48 (m, 1H), 3.77 (s, 1H), 3.27–3.19 (m, 2H), 3.15–3.09
(m, 1H), 2.82–2.74 (m, 1H), 2.68–2.63 (m, 1H), 2.63–2.56
(m, 1H), 2.07–1.98 (m, 1H); 13C NMR (100 MHz, CDCl3,
24ꢀC, δ) 211.4 (C), 135.6 (CH), 132.5 (CH), 131.1 (CH),
124.3 (CH), 71.2 (CH), 52.8 (CH), 49.8 (CH), 42.7 (CH), 38.4
(CH2), 34.4 (CH); IR (neat, cm−1) 3,458, 3,049, 2,944, 2,847,
2,847, 2,360, 1,717, 1,441, 1,353, 1,239, 1,191, 1,136, 1,090,
1,036, 979, 954, 835, 768, 727, 695, 593, 502; HRMS (EI) m/z
calcd for C11H12O2 [M]+ 176.0837, found 176.0839.
4.9 | (2aS*,4aS*,7aR*,7bR*)-1,2a,4a,7,7a,
7b-hexahydro-2H-cyclobuta[e]inden-
2-one (11a)
White solid, 8 mg, 16% yield; Rf = 0.45 (silica gel,
1
EtOAc: n-Hexane = 1:20); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.84–5.80 (m, 1H), 5.76–5.68 (m, 1H), 5.68–5.62
(m, 1H), 5.57 (ddd, J = 10.2, 4.7, 2.2 Hz, 1H), 5.64 (m,
1H), 3.22–3.13 (m, 1H), 3.13–3.01 (m, 2H), 2.77–2.56
(m, 2H), 2.41 (dddd, J = 16.0, 8.3, 2.8, 1.4 Hz, 1H),
13
2.10–2.05 (m, 1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ)
205.9 (C), 132.7 (CH2), 130.3 (CH2), 128.7 (CH2), 117.4
(CH2), 56.9 (CH), 50.3 (CH2), 40.4 (CH), 36.9 (CH), 36.8
(CH2), 24.3 (CH). IR (neat, cm−1) 2,905, 2,354, 1,718,
1,457, 987, 936, 921, 894, 867, 747, 679, 544; HRMS
(ESI) m/z calcd for C11H12O [M]+ 160.0888, found
160.0890.
4.12 | (3aR*,4R*,7S*,7aS*,9S*)-9-hydroxy-
3a,4,7,7a-tetrahydro-1H-4,7-ethanoinden-
8-one (14a)
White solid, 122 mg, 69% yield; Rf = 0.2 (silica gel,
EtOAc: n-Hexane = 1:2); 1H NMR (400 MHz, CDCl3,

HUNG ET AL.
9
24ꢀC, δ) 6.36–6.31 (m, 1H), 6.12–6.05 (m, 1H), 5.63–5.58
(m, 1H), 5.56–5.52 (m, 1H), 3.66 (d, J = 3.3 Hz, 1H),
3.44–3.36 (m, 1H), 3.30–3.20 (m, 1H), 3.14–3.09 (m, 1H),
2.79–2.70 (m, 1H), 2.61–2.50 (m, 2H), 2.09–2.00 (m, 1H);
13C NMR (75 MHz, CDCl3, 24ꢀC, δ) 212.5 (C), 134.9
(CH), 132.0 (CH), 131.8 (CH), 126.1 (CH), 70.7 (CH), 51.9
(CH), 44.7 (CH), 43.3 (CH), 39.2 (CH), 38.2(CH2); IR
(neat, cm−1) 3,448, 3,046, 2,964, 2,905, 2,842, 2,360, 1,722,
1,437, 1,401, 1,358, 1,330, 1,271, 1,213, 1,192, 1,147, 1,088,
980, 961, 924, 854, 824, 798, 754, 730, 702, 687, 559, 789;
HRMS (EI) m/z calcd for C11H12O2 [M]+ 176.0837, found
176.0838.
4.15 | (3aR*,4R*,7S*,7aS*,9R*)-9-hydroxy-
4-methyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (13b)
White solid, 172 mg, 96% yield; Rf = 0.43 (silica gel,
1
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.05 (t, J = 7.3 Hz, 1H), 5.94 (d, J = 7.9 Hz, 1H),
5.77–5.73 (m, 1H), 5.62 (dd, J = 5.9, 2.6 Hz, 1H), 3.47 (d,
J = 2.7 Hz, 1H), 3.22 (d, J = 6.8 Hz, 1H), 2.93–2.77 (m,
2H), 2.66–2.56 (m, 1H), 2.09–1.99 (m, 1H), 1.38 (s, 3H),
13
1.26 (s, 1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 140.3
(CH), 133.9 (CH), 129.0 (CH), 124.2 (CH), 74.8 (CH), 56.4
(CH), 52.5 (CH), 45.1 (C), 38.7 (CH2), 35.3 (CH), 18.3
(CH3); IR (neat, cm−1) 3,437, 304, 2,962, 2,927, 2,359,
1,715, 1,437, 1,375, 1,308, 1,241, 1,206, 1,139, 1,103, 1,079,
1,004, 984, 940, 926, 912, 845, 787, 773, 741, 689, 640,
552, 511, 501; HRMS (ESI) m/z calcd for C12H14O2 [M
+ Na]+ 213.0891, found 213.0888.
4.13 | (3aR*,4R*,7S*,7aS*,9R*)-
8,8-dimethoxy-4-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-9-ol (S1b)
White solid, 533 mg, 35% yield; Rf = 0.30 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.95–5.90 (m, 1H), 5.67–5.64 (m, 1H), 5.55–5.52
(m, 1H), 5.49–5.46 (m, 1H), 3.25 (d, J = 6.8 Hz, 1H), 3.20
(d, J = 1.1 Hz, 3H), 3.17 (d, J = 1.1 Hz, 3H), 2.85 (dd,
J = 7.0, 1.0 Hz, 1H), 2.79 (dd, J = 6.6, 2.9 Hz, 1H),
2.77–2.69 (m, 1H), 2.54–2.47 (m, 1H), 2.44–2.32 (m, 1H),
1.84–1.73 (m, 1H), 1.18 (d, J = 1.1 Hz, 3H); 13C NMR
(75 MHz, CDCl3, 24ꢀC, δ) 137.2 (CH), 132.6 (CH), 130.0
(CH), 127.2 (CH), 103.1 (C), 77.8 (CH), 55.5 (CH), 49.7
(CH3), 49.1 (CH3), 44.5 (CH), 42.5 (C), 38.6 (CH2), 34.6
(CH), 18.9 (CH3); IR (neat, cm−1) 3,671, 3,515, 2,950,
2,845, 2,351, 1,718, 1,371, 1,295, 1,185, 1,121, 1,074,
951, 852, 820, 755, 681, 653, 610; HRMS (HR-ESI) m/z
calcd for C14H20O3 [M + Na]+ 259.1310, found 259.1315.
4.16 | (3aR*,4R*,7S*,7aS*,9S*)-9-hydroxy-
4-methyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (14b)
White solid, 301 mg, 92% yield; Rf = 0.45 (silica gel,
1
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.12–6.03 (m, 2H), 5.71–5.62 (m, 2H), 3.40 (s,
1H), 3.25 (dd, J = 5.2, 2.6 Hz, 1H), 3.20–3.13 (m, 1H),
2.84–2.73 (m, 1H), 2.57 (dd, J = 17.3, 1.7 Hz, 1H),
2.12–2.00 (m, 1H), 1.37 (s, 3H), 1.32–1.22 (m, 1H); 13C
NMR (75 MHz, CDCl3, 24ꢀC, δ) 212.9 (C), 140.6 (CH),
132.9 (CH), 130.3 (CH), 125.2 (CH), 75.2 (CH), 51.7 (CH),
49.8 (CH), 45.7 (C), 41.5 (CH), 38.2 (CH), 18.7 (CH3); IR
(neat, cm−1) 3,674, 3,504, 2,959, 2,898, 2,840, 2,359, 1,718,
1,457, 1,378, 1,298, 1,245, 1,230, 1,195, 1,164, 1,128, 1,078,
1,045, 955, 926, 859, 823, 758, 729, 689, 657, 618, 518;
HRMS (EI) m/z calcd for C12H14O2 [M]+ 190.0994, found
190.0997.
4.14 | (3aR*,4R*,7S*,7aS*,9S*)-
8,8-dimethoxy-4-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-9-ol (S2b)
White solid, 343 mg, 23% yield; Rf = 0.28 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.93–5.89 (m, 1H), 5.73–5.69 (m, 1H), 5.50 (d,
J = 1.7 Hz, 2H), 3.29 (d, J = 1.7 Hz, 3H), 3.12 (d,
J = 14.3 Hz, 1H), 3.06 (d, J = 1.9 Hz, 3H), 2.81–2.74 (m,
3H), 2.58–2.46 (m, 1H), 2.37–2.28 (m, 1H), 1.84–1.76 (m,
1H), 1.14 (d, J = 1.7 Hz, 3H); 13C NMR (75 MHz, CDCl3,
24ꢀC, δ) 138.0 (CH), 131.9 (CH), 131.2 (CH), 128.4 (CH),
100.5 (C), 75.5 (CH), 48.8 (CH), 48.4 (CH3), 48.3 (CH3),
43.8 (CH), 41.7 (C), 37.8 (CH2), 35.8 (CH), 19.3 (CH3); IR
(neat, cm−1) 3,675, 3,511, 2,951, 2,840, 2,350, 1,720, 1,378,
1,290, 1,190, 1,128, 1,078, 955, 859, 821, 752, 689, 651,
610; HRMS (HR-ESI) m/z calcd for C14H20O3 [M + Na]+
259.1310; found 259.1313.
4.17 | (3aS*,4S*,7R*,7aS*,9R*)-
8,8-dimethoxy-5-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-9-ol (S1c)
White solid, 210 mg, 45% yield; Rf = 0.33 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.63 (d, J = 6.4 Hz, 1H), 5.58–5.54 (m, 1H), 5.40
(dt, J = 5.7, 2.4 Hz, 1H), 3.72 (dd, J = 6.6, 2.7 Hz, 1H),
3.28 (s, 3H), 3.25 (s, 3H), 3.06 (d, J = 6.6 Hz, 1H), 2.93
(ddd, J = 8.7, 4.1, 2.0 Hz, 1H), 2.74 (dd, J = 6.6, 2.8 Hz,
1H), 2.72–2.67 (m, 1H), 2.55 (dd, J = 2.4 Hz, 1H),
2.47–2.42 (m, 1H), 1.89 (dddd, J = 16.9, 6.6, 4.3, 2.4 Hz,
1H), 1.73 (d, J = 1.7 Hz, 3H); 13C NMR (75 MHz, CDCl3,

10
HUNG ET AL.
24ꢀC, δ) 141.3 (C), 131.9 (CH), 131.3 (CH), 118.5 (CH),
102.9 (C), 74.4 (CH), 49.7 (CH3), 49.3 (CH3), 49.1 (2xCH),
42.4 (CH), 38.5 (CH2), 33.5 (CH), 23.1 (CH3); IR (neat,
cm−1) 3,648, 2,956, 1,653, 1,443, 1,394, 1,234, 1,125, 1,069,
1,049, 991, 970, 946, 918, 894, 827, 797, 754, 727, 697,
612, 586, 529; HRMS (EI) m/z calcd for C14H20O3 [M
+ Na]+ 259.1310, found 259.1311.
24ꢀC, δ) 5.71–5.63 (m, 1H), 5.64–5.60 (m, 1H), 5.53–5.50
(m, 1H), 3.67 (d, J = 3.4 Hz, 1H), 3.43–3.36 (m, 1H), 3.11
(dd, J = 6.0, 3.1 Hz, 1H), 2.89–2.87 (m, 1H), 2.78–2.66 (m,
2H), 2.61–2.48 (m, 1H), 2.10–2.05 (m, 1H); 13C NMR
(75 MHz, CDCl3, 24ꢀC, δ) 213.6 (C), 143.9 (C), 132.1
(CH), 131.3 (CH), 117.8 (CH), 71.3 (CH), 51.3 (CH), 48.5
(CH), 44.6 (CH), 39.9 (CH), 38.3 (CH2), 22.0 (CH3); IR
(neat, cm−1) 3,399, 2,902, 2,361, 1,715, 1,442, 1,262, 1,216,
1,168, 1,110, 1,075, 1,042, 978, 946, 890, 789, 705, 669,
646, 593; HRMS (EI) m/z calcd for C12H14O2 [M]+
190.0994, found 190.0995.
4.18 | (3aR*,4S*,7R*,7aS*,9S*)-
8,8-dimethoxy-5-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-9-ol (S2c)
White solid, 224 mg, 47% yield; Rf = 0.35 (silica gel, EtOAc:
4.21 | (3aR*,4S*,7R*,7aS*,9R*)-9-hydroxy-
5-vinyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (13d)
1
n-Hexane = 1:5); H NMR (400 MHz, CDCl3, 24ꢀC, δ)
5.71–5.63 (m, 1H), 5.64–5.60 (m, 1H), 5.53–5.50 (m, 1H),
3.67 (d, J = 3.4 Hz, 1H), 3.43–3.36 (m, 1H), 3.11 (dd, J = 6.0,
3.1 Hz, 1H), 2.89–2.87 (m, 1H), 2.78–2.66 (m, 2H), 2.61–2.48
(m, 1H), 2.1–2.05 (m, 1H); 13C NMR (75 MHz, CDCl3,
24ꢀC, δ) 213.6 (C), 143.9 (C), 132.1 (CH), 131.3 (CH), 117.8
(CH), 71.3 (CH), 51.3 (CH), 48.5 (CH), 44.6 (CH), 39.9
(CH), 38.3 (CH2), 22.0 (CH3); IR (neat, cm−1) 3,399, 2,902,
2,361, 1,715, 1,442, 1,262, 1,216, 1,168, 1,110, 1,075, 1,042,
978, 946, 890, 789, 705, 669, 646, 593; HRMS (EI) m/z calcd
for C12H14O2 [M]+ 190.0994, found 190.0995.
Colorless liquid, 130 mg, 43% yield; Rf = 0.40 (silica gel,
1
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ)6.43 (dd, J = 17.4, 10.7 Hz, 1H), 5.96–5.90 (m,
1H), 5.65 (dd, J = 5.8, 2.3 Hz, 1H), 5.45–5.42 (m, 1H),
5.37 (d, J = 17.4 Hz, 1H), 5.10 (d, J = 10.7 Hz, 1H), 3.87
(d, J = 2.5 Hz, 1H), 3.49 (dd, J = 2.6 Hz, 1H), 3.41–3.27
(m, 1H), 3.23 (dd, J = 6.8, 2.7 Hz, 1H), 2.83–2.76 (m,
1H), 2.72–2.55 (m, 3H), 2.11–2.04 (m, 1H); 13C NMR
(75 MHz, CDCl3, 24ꢀC, δ) 210.2 (C), 145.0 (C), 135.7
(CH), 132.7 (CH), 130.2 (CH), 121.1 (CH), 114.2 (CH2),
71.5 (CH), 52.9 (CH), 49.5 (CH), 41.6 (CH), 38.6 (CH2),
34.3 (CH); IR (neat, cm−1) 3,423, 2,900, 2,360, 2,341,
1,731, 1,395, 1,258, 1,054, 700, 517, 508; HRMS (HR-
APCI) m/z calcd for C13H15O2 [M + H]+ 203.1072, found
203.1072.
4.19 | (3aR*,4S*,7R*,7aS*,9R*)-9-hydroxy-
5-methyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (13c)
White solid, 83 mg, 67% yield; Rf = 0.35 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.69 (dd, J = 5.7, 2.2 Hz, 1H), 5.50–5.46 (m, 1H),
3.76 (d, J = 2.2 Hz, 1H), 3.25–3.19 (m, 1H), 3.09 (dd,
J = 6.7, 2.6 Hz, 1H), 2.89 (q, J = 2.5 Hz, 1H), 2.77–2.70
(m, 1H), 2.64 (d, J = 2.3 Hz, 1H), 2.59 (ddd, J = 17.2, 9.9,
2.1 Hz, 1H), 1.80 (d, J = 1.7 Hz, 4H), 1.73 (ddd, J = 10.6,
4.22 | (3aR*,4S*,7R*,7aS*,9S*)-9-hydroxy-
5-vinyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (14d)
13
6.0, 1.7 Hz, 1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ)
Colorless liquid, 110 mg, 37% yield; Rf = 0.40 (silica gel,
1
211.7 (C), 145.5 (C), 132.8 (CH), 130.2 (CH), 115.6 (CH),
71.8 (CH), 52.1 (CH), 49.7 (CH), 48.1 (CH), 38.4 (CH2),
34.0 (CH), 22.8 (CH3); IR (neat, cm−1) 3,469, 3,043, 2,899,
1,716, 1,437, 1,177, 1,081, 953, 764, 770, 718, 693, 518;
HRMS (EI) m/z calcd for C12H14O2 [M]+ 190.0994, found
190.0992.
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.43–6.32 (m, 1H), 5.93 (d, J = 6.1 Hz, 1H),
5.60–5.55 (m, 1H), 5.49–5.44 (m, 1H), 5.33 (d,
J = 17.4 Hz, 1H), 5.10 (dd, J = 10.8, 1.2 Hz, 1H), 3.64 (d,
J = 3.0 Hz, 1H), 3.51–3.46 (m, 2H), 3.26 (dd, J = 6.3,
3.0 Hz, 1H), 2.96 (s, 1H), 2.85–2.75 (m, 1H), 2.62–2.51 (m,
1H), 2.16–2.07 (m, 1H); 13C NMR (75 MHz, CDCl3, 24ꢀC,
δ) 212.7 (C), 144.3 (C), 134.8 (CH), 131.9 (CH), 131.3
(CH), 122.8 (CH), 113.7 (CH2), 71.6 (CH), 52.1 (CH), 44.4
4.20 | (3aR*,4S*,7R*,7aS*,9S*)-9-hydroxy-
5-methyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-8-one (14c)
(CH), 42.0 (CH), 40.2 (CH), 38.4 (CH2); IR (neat, cm−1
)
3,395, 3,645, 2,938, 2,359, 2,341, 1,709, 1,626, 1,445, 1,411,
1,255, 1,185, 1,134, 1,082, 997, 986, 973, 903, 864, 819,
773, 700, 643, 532, 510; HRMS (HR-APCI) m/z calcd for
C13H15O2 [M + H]+ 203.1072, found 203.1079.
White solid, 130 mg, 76% yield; Rf = 0.35 (silica gel,
EtOAc: n-Hexane = 1:5); 1H NMR (400 MHz, CDCl3,

HUNG ET AL.
11
13
4.23 | (3aR*,4S*,7R*,7aS*)-8,8-dimethoxy-
9-oxo-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoindene-5-carbaldehyde (15)
2.11–1.99 (m, 1H); C NMR (75 MHz, CDCl3, 24ꢀC, δ)
203.5 (C), 137.7 (C), 134.7 (CH), 132.9 (CH), 129.5 (CH),
128.3 (CH), 113.2 (CH2), 95.0 (C), 51.2 (CH), 50.5 (CH3),
49.7 (CH3), 49.2 (CH), 44.0 (CH), 38.4 (CH2), 33.8 (CH);
IR (neat, cm−1) 3,674, 3,395, 2,938, 2,359, 2,341, 1,709,
1,626, 1,445, 1,411, 1,215, 1,181, 1,130, 1,081, 995, 901,
865, 810, 771, 643, 532, 510; HRMS (APCI) m/z calcd for
C15H18O3 [M + H]+ 247.1329, found 247.1333.
To a stirred solution of 7d (0.193 g, 0.578 mmol) in ethyl
acetate (19 ml) was sequentially added 1 N HCl solution
(19 ml) at room temperature. After being stirred for 2 hr,
the reaction mixture was quenched with saturated aque-
ous NaHCO3 solution and extracted with CH2Cl2 several
times. The combined organic layers were dried over
MgSO4, filtered, and concentrated. The residue was puri-
fied by flash chromatography on silica gel (EtOAc: n-
Hexane = 1:5 ! 1:3) to afford 15 (140 mg, 97% yield) as a
white solid.
4.25 | General procedure of the
photoreaction: Method A for the synthesis
of 17a and 18a (synthesis of 18a as example)
Rf = 0.40 (silica gel, EtOAc: n-Hexane = 1:3); 1H
NMR (400 MHz, CDCl3, 24ꢀC, δ) 9.42 (s, 1H), 7.13 (dd,
J = 6.8, 1.7 Hz, 1H), 5.54 (dd, J = 5.6, 2.3 Hz, 1H),
5.31–5.21 (m, 1H), 3.72 (t, J = 2.2 Hz, 1H), 3.44 (dd,
J = 6.9, 3.0 Hz, 2H), 3.32 (s, 3H), 3.20 (d, J = 3.8 Hz, 3H),
2.94–2.88 (m, 1H), 2.58–2.50 (m, 1H), 1.99–1.94 (m, 1H);
13C NMR (75 MHz, CDCl3, 24ꢀC, δ) 201.6 (C), 188.6
(CH), 149.5 (CH), 140.5 (C), 133.1 (CH), 129.5 (CH), 94.6
(C), 50.7 (CH3), 49.6 (CH3), 49.5 (CH), 48.3 (CH), 45.5
(CH), 38.4 (CH2), 33.7 (CH); IR (neat, cm−1) 3,398, 3,046,
2,938, 2,360, 2,341, 1,717, 1,674, 1,626, 1,445, 1,411, 1,254,
1,185, 1,132, 1,084, 1,018, 986, 903, 864, 819, 789, 776,
736, 719, 663, 638, 594; HRMS (APCI) m/z calcd for
C14H16O4 [M + H]+ 249.1127, found 249.1124.
To a solution of 13a (176 mg, 1.00 mmol), imidazole
(204 mg, 3.00 mmol) and
a
catalytic amount of
4-Dimethylaminopyridine (DMAP) in dry CH2Cl2 (5 ml)
were slowly added TBSCl (226 mg, 1.50 mmol) at 0ꢀC.
The reaction mixture was then heated at reflux tempera-
ture for 12 hr. The reaction mixture was cooled to room
temperature and quenched with saturated aqueous
NH4Cl. The layers were separated and the aqueous layer
was extracted with CH2Cl2. The combined organic layers
were washed with brine, dried over MgSO4, filtered, and
concentrated under reduced pressure. The residue was
purified by flash chromatography on silica gel (EtOAc: n-
Hexane = 1:39) to afford S3a (288 mg, 98% yield) as a col-
orless oil. To a solution of S3a (102 mg, 0.305 mmol) in
acetonitrile (70 ml) was transferred into the quartz tube
and degassed by purging with N2 for 45 min. The reac-
tion mixture was irradiated with a broad band centered
at 306 nm in a Rayonet-type photoreactor and stirred for
17 hr. The reaction mixture was then concentrated under
reduced pressure. The residue was purified by flash chro-
matography on silica gel (n-Hexane) to afford 18a
(52 mg, 57% yield) as a sticky colorless oil.
4.24 | (3aR*,4S*,7R*,7aS*)-8,8-dimethoxy-
5-vinyl-3a,4,7,7a-tetrahydro-1H-
4,7-ethanoinden-9-one (16)
Methyltriphenyl phosphonium
bromide (0.313 g,
0.877 mmol) and sodium hydride (54 mg, 2.34 mmol) in
anhydrous THF (6 ml) was stirred at 0ꢀC. After stirring
for 30 min, the suspension was added a solution of 15
(0.145 g, 0.584 mmol) in anhydrous THF (2 ml) and then
stirred at room temperature for 2 hr. The mixture was
quenched by saturated aqueous NH4Cl solution,
extracted with ether. The combined organic layers were
dried over MgSO4, filtered, and concentrated. The residue
was was purified by flash chromatography on silica gel
(EtOAc: n-Hexane = 1:10 ! 1:3) to afford 16 (89 mg,
62% yield) as a white solid.
4.26 | General procedure of the
photoreaction: Method B for the synthesis
of 17b-d and 18b-d (synthesis of 17b and 18b
as example)
To a solution of 13b (195 mg, 1.00 mmol), imidazole
(204 mg, 3.00 mmol) and a catalytic amount of DMAP in
dry CH2Cl2 (5 ml) were slowly added TBSCl (226 mg,
1.50 mmol) at 0ꢀC. The reaction mixture was then heated
at reflux temperature for 12 hr. The reaction mixture was
cooled to room temperature and quenched with saturated
aqueous NH4Cl. The layers were separated and the aque-
ous layer was extracted with CH2Cl2. The combined
organic layers were washed with brine, dried over
MgSO4, filtered, and concentrated under reduced
Rf = 0.30 (silica gel, EtOAc: n-Hexane = 1:3); 1H
NMR (400 MHz, CDCl3, 24ꢀC, δ) 6.35 (dd, J = 17.5,
10.8 Hz, 1H), 6.12–6.05 (m, 1H), 5.66–5.59 (m, 1H), 5.34
(dd, J = 5.6, 2.4 Hz, 1H), 5.19 (d, J = 17.4 Hz, 1H), 5.01
(dd, J = 10.8, 0.8 Hz, 1H), 3.51 (s, 1H), 3.37 (d,
J = 0.7 Hz, 3H), 3.30 (d, J = 0.7 Hz, 4H), 3.16 (dd, J = 6.8,
3.0 Hz, 1H), 2.97–2.85 (m, 1H), 2.61–2.48 (m, 1H),

12
HUNG ET AL.
pressure. The residue was purified by flash chromatogra-
phy on silica gel (EtOAc: n-Hexane = 1:20 ! 1:10) to
afford S3b (257 mg, 84% yield) as a white solid. To a solu-
tion of S3b (160 mg, 0.525 mmol) in acetonitrile (160 ml)
was transferred into the quartz tube and degassed by
purging with N2 for 45 min. The reaction mixture was
irradiated with a broad band centered at 306 nm in a
Rayonet-type photoreactor and stirred for 4.5 hr. The
reaction mixture was then concentrated under reduced
pressure. The residue was purified by flash chromatogra-
phy on silica gel (n-Hexane) to afford two colorless oil
17b (12 mg, 8% yield) and 18b (95 mg, 65% yield).
(APCI) m/z calcd for C16H27OSi [M + H]+ 263.1831
found 263.1828.
4.29 | (3aR*,4R*,7S*,7aS*,9S*)-9-((tert-
butyldimethylsilyl)oxy)-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S4a)
Colorless oil, 288 mg, 98% yield; Rf = 0.33 (silica gel,
1
EtOAc: n-Hexane = 1:39); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.25 (s, 1H), 6.08 (d, J = 7.6 Hz, 1H), 5.63 (dd,
J = 5.7, 2.2 Hz, 1H), 5.55 (d, J = 2.2 Hz, 1H), 3.64 (d,
J = 3.6 Hz, 1H), 3.61–3.43 (m, 1H), 3.12 (dd, J = 5.7,
2.1 Hz, 1H), 2.99–2.71 (m, 1H), 2.56 (ddd, J = 17.2, 10.1,
1.6 Hz, 2H), 2.07–1.93 (m, 1H), 0.90 (s, 9H), 0.12 (d,
4.27 | (3aR*,4R*,7S*,7aS*,9R*)-9-((tert-
Butyldimethylsilyl)oxy)-3a,4,7,7a-
13
J = 8.8 Hz, 6H); C NMR (100 MHz, CDCl3, 24ꢀC, δ)
tetrahydro-1H-4,7-ethanoinden-8-one (S3a)
208.8 (C), 134.8 (CH), 132.2 (CH), 132.0 (CH), 126.9
(CH), 70.9 (CH), 52.7 (CH), 45.0 (CH), 44.7 (CH), 38.4
(CH2), 38.1 (CH), 25.8 (CH3)x3, 18.2 (C), −4.5 (CH3),
−5.2 (CH3); IR (neat, cm−1) 3,053, 2,929, 2,855, 1,739,
1,471, 1,443, 1,389, 1,360, 1,295, 1,254, 1,216, 1,120, 1,007,
983, 939, 924, 887, 839, 780, 754, 681; HRMS (APCI) m/z
calcd for C17H27O2Si [M + H]+ 291.1780, found 219.1771.
Colorless oil, 288 mg, 98% yield; Rf = 0.33 (silica gel,
1
EtOAc: n-Hexane = 1:39); H NMR (400 MHz, CDCl3,
24ꢀC, δ): δ 6.26 (t, J = 7.1 Hz, 1H), 6.06 (t, J = 7.2 Hz,
1H), 5.66 (dd, J = 5.6, 2.2 Hz, 1H), 5.48 (dd, J = 5.4,
2.3 Hz, 1H), 3.69 (s, 1H), 3.11 (dd, J = 14.7, 7.7 Hz, 2H),
2.90 (d, J = 6.1 Hz, 1H), 2.72 (t, J = 9.6 Hz, 1H), 2.57 (dd,
J = 16.1, 9.3 Hz, 1H), 2.10–1.90 (m, 1H), 1.25 (s, 3H), 0.88
(s, 6H), 0.12 (s, 2H), 0.07 (s, 2H); 13C NMR (100 MHz,
CDCl3, 24ꢀC, δ) 209.1 (C), 135.1 (CH), 132.7 (CH), 131.0
(CH), 124.2 (CH), 72.1 (CH), 53.1 (CH), 49.5 (CH), 44.3
(CH), 38.6 (CH2), 35.2 (CH), 25.8 (CH3)x3, 18.3 (C), −4.5
(CH3), −5.2 (CH3); IR (neat, cm−1) 3,736, 3,455, 3,054,
2,928, 2,855, 2,361, 1,736, 1,624, 1,472, 1,463, 1,443, 1,388,
1,359, 1,312, 1,252, 1,224, 1,189, 1,129, 1,096, 1,068, 1,039,
1,006, 991, 972, 939, 926, 888, 837, 779, 696, 681, 648;
HRMS (APCI) m/z calcd for C17H27O2Si [M + H]+
291.1780, found 219.1772.
4.30 | tert-butyl
(((1S*,1aS*,3aS*,6aS*,6bR*)-1,1a,3a,4,6a,6b-
hexahydrocyclopropa[e]inden-1-yl)oxy)
dimethylsilane (17a)
Sticky colorless oil, 48 mg, 52% yield; Rf = 0.23 (silica gel,
n-Hexane); 1H NMR (400 MHz, CDCl3, 24ꢀC, δ)
5.75–5.62 (m, 2H), 5.32 (dd, J = 10.1, 2.3 Hz, 1H), 3.52 (t,
J = 6.6 Hz, 1H), 3.14–3.09 (m, 1H), 2.77–2.60 (m, 2H),
2.08 (dt, J = 13.8, 2.0 Hz, 1H), 1.29–1.17 (m, 3H), 0.89 (s,
9H), 0.06 (d, J = 22.2 Hz, 6H); 13C NMR (100 MHz,
CDCl3, 24ꢀC, δ) 135.3 (CH), 130.6 (CH), 128.2 (CH),
119.6 (CH), 55.8 (CH), 41.5 (CH2), 37.9 (CH), 36.7 (CH),
25.9 (CH3)x3, 18.1 (C), 17.7 (CH), 14.5 (CH), −5.1 (CH3),
−5.4 (CH3); IR (neat, cm−1) 3,049, 3,016, 2,955, 2,928,
2,855, 1,653, 1,471, 1,444, 1,404, 1,351, 1,284, 1,251, 1,224,
1,211, 1,134, 1,105, 1,053, 1,006, 961, 875, 839, 777,
734, 672; HRMS (APCI) m/z calcd for C16H27OSi [M
+ H]+ 263.1831, found 263.1828.
4.28 | tert-butyl
(((1R*,1aS*,3aS*,6aS*,6bR*)-1,1a,3a,4,6a,6b-
hexahydrocyclopropa[e]inden-1-yl)oxy)
dimethylsilane (18a)
Sticky colorless oil, 52 mg, 57% yield; Rf = 0.13 (silica gel,
1
n-Hexane); H NMR (300 MHz, CDCl3, 24ꢀC, δ) 5.97
(ddd, J = 9.9, 4.8, 1.9 Hz, 1H), 5.71–5.52 (m, 2H), 5.08
(dd, J = 10.1, 2.2 Hz, 1H), 3.29 (d, J = 6.3 Hz, 1H),
3.06–2.97 (m, 1H), 2.77–2.51 (m, 2H), 2.01 (d,
J = 15.0 Hz, 1H), 1.48–1.32 (m, 2H), 0.90 (s, 9H), 0.11 (s,
4.31 | (3aR*,4R*,7S*,7aS*,9R*)-9-((tert-
butyldimethylsilyl)oxy)-4-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S3b)
13
6H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 135.2, 128.2,
127.9, 124.5, 61.0, 41.2, 39.7, 34.8, 25.8, 23.5, 19.6, 18.0,
−4.9; IR (neat, cm−1) 3,371, 3,021, 2,928, 2,856, 1,725,
1,471, 1,424, 1,389, 1,361, 1,348, 1,308, 1,254, 1,219, 1,146,
1,046, 1,006, 962, 940, 900, 838, 778, 723, 695, 664; HRMS
White solid, 257 mg, 84% yield; Rf = 0.45 (silica gel,
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 6.01–5.97 (m, 1H), 5.91–5.86 (m, 1H), 5.72–5.70
1

HUNG ET AL.
13
(m, 1H), 5.62–5.57 (m, 1H), 3.36 (s, 1H), 3.14–3.06 (m,
1H), 2.77–2.75 (m, 2H), 2.64–2.50 (m, 1H), 2.06–1.99(m,
1H), 1.27 (s, 3H), 0.87 (d, J = 0.8 Hz, 9H), 0.11 (d,
4.34 | tert-Butyldimethyl
(((1R*,1aS*,3aS*,6aS*,6bR*)-6b-methyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (18b)
13
J = 0.7 Hz, 6H); C NMR (75 MHz, CDCl3, 24ꢀC, δ)
209.7(C), 139.8 (CH), 133.6 (CH), 129.4 (CH), 123.4 (CH),
75.5 (CH), 55.6 (CH), 52.8 (CH), 45.6 (C), 38.7 (CH2), 36.4
(CH), 25.9 (3xCH3), 19.2 (CH), 18.4 (C), −4.1 (CH3), −5.2
(CH3); IR (neat, cm−1) 2,953, 2,926, 2,854, 2,359, 1,720,
1,462, 1,359, 1,252, 1,218, 1,107, 1,051, 1,007, 990, 956,
937, 923, 853, 830, 768, 746, 707, 686, 635, 551, 519, 509;
HRMS (HR-APCI) m/z calcd for C18H29O2 [M + H]+
305.1937, found 305.1940.
Colorless liquid, 19 mg, 13% yield; Rf = 0.45 (silica gel, n-
1
Hexane); H NMR (400 MHz, CDCl3, 24ꢀC, δ) 6.00 (ddd,
J = 10.1, 5.7, 2.6 Hz, 1H), 5.96–5.89 (m, 1H), 5.69–5.65
(m, 1H), 4.95 (dd, J = 10.0, 2.1 Hz, 1H), 3.16 (dd, J = 2.2,
0.7 Hz, 1H), 2.78–2.68 (m, 1H), 2.68–2.56 (m, 1H),
2.10–2.01 (m, 1H), 1.35–1.22 (m, 4H), 1.00 (dd, J = 5.7,
2.2 Hz, 1H), 0.95–0.86 (m, 9H), 0.13–0.06 (m, 6H); 13C
NMR (75 MHz, CDCl3, 24ꢀC, δ) 133.1 (CH), 129.0 (CH),
126.9 (CH), 126.6 (CH), 77.1 (CH), 64.1 (CH), 46.3 (CH2),
36.7 (CH), 26.5 (3xCH3), 25.9 (CH3), 25.9 (CH), 23.9 (C),
18.1 (C), 16.3 (CH3), −4.9 (CH3), −5.0 (CH3); IR (neat,
cm−1) 2,930, 2,851, 1,720, 1,255, 1,081, 832, 775, 419.
4.32 | (3aR*,4R*,7S*,7aS*,9S*)-9-((tert-
butyldimethylsilyl)oxy)-4-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S4b)
White solid, 364 mg, 73% yield; Rf = 0.45 (silica gel, EtOAc:
1
n-Hexane = 1:10); H NMR (400 MHz, CDCl3, 24ꢀC, δ)
4.35 | (3aR*,4S*,7R*,7aS*,9R*)-9-((tert-
butyldimethylsilyl)oxy)-5-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S3c)
6.05–6.00 (m, 1H), 5.95–5.90 (m, 1H), 5.64–5.62 (m, 1H),
5.59–5.56 (m, 1H), 3.31 (d, J = 1.2 Hz, 1H), 3.27–3.19 (m,
1H), 3.07–3.05 (m, 1H), 2.83–2.72 (m, 1H), 2.51 (dd,
J = 17.2, 10.1, 1.8 Hz, 1H), 2.05–1.94 (m, 1H), 1.25 (d,
J = 1.2 Hz, 3H), 0.88 (d, J = 1.3 Hz, 9H), 0.12 (d, J = 1.2 Hz,
3H), 0.07 (d, J = 1.1 Hz, 3H); 13C NMR (75 MHz, CDCl3,
24ꢀC, δ) 140.3 (CH), 132.7 (CH), 130.5 (CH), 125.9 (CH),
75.1 (CH), 52.8 (CH), 50.3 (CH), 46.1 (C), 39.3 (CH), 38.4
(CH2), 25.9 (3xCH3), 19.6 (CH), 18.4 (C), −4.0 (CH3), −5.2
(CH3); IR (neat, cm−1) 2,956, 2,928, 2,856, 2,360, 1,738,
1,460, 1,362, 1,251, 1,105, 1,090, 1,051, 939, 883, 836, 778,
754, 739, 682, 662, 603; HRMS (HR-APCI) m/z calcd for
C18H29O2 [M + H]+ 305.1937, found 305.1932.
White solid, 221 mg, 98% yield; Rf = 0.38 (silica gel,
1
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
24ꢀC, δ) 5.67–5.64 (m, 2H), 5.48–5.44 (m, 1H), 3.68 (d,
J = 2.6 Hz, 1H), 3.16–3.06 (m, 1H), 2.97 (dd, J = 6.6,
2.8 Hz, 1H), 2.73–2.62 (m, 2H), 2.60–2.49 (m, 1H),
2.12–1.99 (m, 1H), 1.79 (d, J = 1.8 Hz, 3H), 0.88 (d,
J = 2.3 Hz, 9H), 0.12 (d, J = 3.2 Hz, 5H); 13C NMR
(75 MHz, CDCl3, 24ꢀC, δ) 209.8 (C), 144.7 (C), 132.7
(CH), 130.4 (CH), 115.1 (CH), 72.3 (CH), 52.4 (CH), 49.8
(CH), 49.1 (CH), 38.5 (CH2), 34.9 (CH), 25.7 (2xCH3),
23.1 (CH3), 18.3 (C), −4.6 (CH3), −5.3 (CH3); IR (neat,
cm−1) 2,928, 2,854, 2,359, 1,732, 1,472, 1,441, 1,360, 1,250,
1,176, 1,138, 1,114, 1,065, 1,005, 980, 835, 777, 740, 696;
HRMS (EI) m/z calcd for C18H28O2Si [M]+ 327.1756,
found 327.1747.
4.33 | tert-butyldimethyl
(((1S*,1aS*,3aS*,6aS*,6bR*)-6b-methyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (17b)
Colorless liquid, 73 mg, 50% yield; Rf = 0.45 (silica gel, n-
4.36 | (3aR*,4S*,7R*,7aS*,9S*)-9-((tert-
butyldimethylsilyl)oxy)-5-methyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S4c)
1
Hexane); H NMR (400 MHz, CDCl3, 24ꢀC, δ) 5.85–5.82
(m, 1H), 5.73–5.61 (m, 2H), 5.23 (dd, J = 10.0, 2.3 Hz,
1H), 3.19 (d, J = 6.5 Hz, 1H), 3.02–2.94 (m, 1H),
2.86–2.81 (m, 1H), 2.72–2.58 (m, 1H), 2.16–2.06 (m, 1H),
1.14 (s, 3H), 1.09 (s, 1H), 0.89 (s, 9H), 0.08 (s, 3H), 0.02 (s,
White solid, 150 mg, 98% yield; Rf = 0.35 (silica gel,
1
EtOAc: n-Hexane = 1:10); H NMR (400 MHz, CDCl3,
13
3H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 132.4 (CH),
24ꢀC, δ) 5.69–5.60 (m, 3H), 5.55–5.48 (m, 1H), 3.65 (d,
J = 3.7 Hz, 1H), 3.50 (d, J = 9.1 Hz, 1H), 2.98 (dd, J = 6.4,
2.9 Hz, 1H), 2.83–2.66 (m, 2H), 2.55 (dd, J = 17.1,
10.0 Hz, 1H), 1.77 (d, J = 1.6 Hz, 3H), 0.91 (d, J = 1.3 Hz,
9H), 0.14 (d, J = 4.1 Hz, 6H); 13C NMR (75 MHz, CDCl3,
24ꢀC, δ) 209.4 (C), 143.8 (C), 132.0 (CH), 131.5 (CH),
118.3 (CH), 70.6 (CH2), 52.4 (CH), 50.2 (CH), 44.8 (CH),
130.4 (CH), 128.9 (CH), 120.6 (CH), 64.0 (CH), 43.5 (CH),
40.8 (CH2), 38.1 (CH), 25.9 (3xCH3), 23.6 (CH3), 23.0
(CH), 20.7 (C), 18.2 (C), −5.1 (CH3), −5.4 (CH3); IR (neat,
cm−1) 2,928, 2,856, 1,722, 1,253, 1,086, 836, 778, 411;
HRMS (HR-APCI) m/z calcd for C18H29O2Si [M + H]+
305.1937, found 305.1940.

14
HUNG ET AL.
38.3 (CH2), 37.6 (CH), 25.7 (3xCH3), 22.1 (CH3), 18.2 (C),
−4.5 (CH3), −5.2 (CH3); IR (neat, cm−1) 2,927, 2,855,
2,358, 1,737, 1,471, 1,441, 1,359, 1,251, 1,166, 1,099, 1,005,
906, 835, 777, 702, 688, 645, 582, 518, 510, 502; HRMS
(EI) m/z calcd for C18H28O2Si [M]+ 327.1756, found
327.1750.
24ꢀC, δ) 6.42 (dd, J = 17.4, 10.7 Hz, 1H), 5.88 (dd, J = 6.6,
1.9 Hz, 1H), 5.62 (dd, J = 5.7, 2.2, 1.0 Hz, 1H), 5.41 (dd,
J = 5.6, 2.5 Hz, 1H), 5.29–5.22 (m, 1H), 5.02 (dd, J = 10.7,
0.9 Hz, 1H), 3.77 (d, J = 2.7 Hz, 1H), 3.27 (q, J = 2.6 Hz,
1H), 3.23–3.15 (m, 1H), 3.11 (dd, J = 6.6, 2.8 Hz, 1H),
2.72 (dd, J = 2.5, 1.4 Hz, 1H), 2.61–2.52 (m, 1H),
2.11–2.02 (m, 1H), 0.84 (d, J = 0.8 Hz, 9H), 0.12–0.08 (m,
13
6H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 208.7 (C), 144.5
4.37 | tert-butyldimethyl
(C), 136.2 (CH), 132.4 (CH), 130.4 (CH), 120.7 (CH),
112.9 (CH2), 71.8 (CH), 53.2 (CH), 48.9 (CH), 43.3 (CH),
38.6 (CH2), 35.2 (CH), 25.7 (3xCH3), 18.4 (C), −4.5 (CH3),
−5.3 (CH3); IR (neat, cm−1) 2,925, 2,360, 2,341, 1,734,
1,459, 1,248, 1,114, 1,066, 995, 982, 900, 836, 774, 735,
696; HRMS (HR-APCI) m/z calcd for C19H29O2Si [M
+ H]+ 317.1937, found 317.1942.
(((1R*,1aS*,3aS*,6aS*,6bR*)-1a-methyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (17c)
Colorless liquid, 10 mg, 7% yield; Rf = 0.43 (silica gel, n-
1
Hexane); H NMR (400 MHz, CDCl3, 24ꢀC, δ) 5.63–5.59
(m, 2H), 5.47 (dd, J = 10.1, 2.3 Hz, 1H), 5.34–5.29 (m,
1H), 3.16 (d, J = 6.7 Hz, 1H), 3.07 (d, J = 7.4 Hz, 1H),
2.73–2.68 (m, 1H), 2.68–2.63 (m, 2H), 2.08 (dd, J = 14.9,
2.7 Hz, 1H), 1.10 (s, 3H), 0.89 (s, 8H), 0.07 (s, 3H), 0.01 (s,
4.40 | (3aR*,4S*,7R*,7aS*,9S*)-9-((tert-
butyldimethylsilyl)oxy)-5-vinyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S4d)
13
3H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 135.7 (CH),
130.1 (CH), 127.8 (CH), 125.1 (CH), 62.8 (CH), 41.3
(CH2), 38.5 (CH), 36.6 (CH), 25.9 (3xCH3), 25.8 (CH),
23.4 (CH3), 18.5 (C), 18.1 (C), −5.0 (CH3), −5.5 (CH3); IR
(neat, cm−1) 2,930, 2,815, 2,358, 1,720, 1,465, 1,351, 1,254,
1,106, 837, 789, 670; HRMS (EI) m/z calcd for C17H28OSi
[M]+ 276.1909, found 276.1911.
White solid, 188 mg, 92% yield; Rf = 0.35 (silica gel, EtOAc:
n-Hexane = 1:15); 1H NMR (400 MHz, CDCl3, 24ꢀC, δ) 6.36
(dd, J = 17.4, 10.7 Hz, 1H), 5.92 (dd, J = 6.4, 2.0 Hz, 1H),
5.61–5.58 (m, 1H), 5.48–5.44 (m, 1H), 5.28 (d, J = 17.4 Hz,
1H), 5.08 (d, J = 10.7 Hz, 1H), 3.59 (dd, J = 14.4, 6.4 Hz, 2H),
3.25 (q, J = 2.9 Hz, 1H), 3.14 (dd, J = 6.3, 3.0 Hz, 1H),
2.86–2.79 (m, 1H), 2.63–2.50 (m, 1H), 2.11–2.03 (m, 1H), 0.92
(s, 9H), 0.14 (d, J = 4.4 Hz, 6H); 13C NMR (75 MHz, CDCl3,
24ꢀC, δ) 208.4 (C), 144.2 (C), 135.2 (CH), 131.8 (CH), 131.5
(CH), 123.6 (CH), 113.0 (CH2), 71.1 (CH), 53.2 (CH), 44.5
(CH), 43.6 (CH), 38.4 (CH2), 38.2 (CH), 25.8 (3xCH3), 18.3
(C), −4.5 (CH3), −5.1 (CH3); IR (neat, cm−1) 2,930, 2,356,
2,341, 1,732, 1,459, 1,248, 1,114, 1,066, 995, 982, 900, 836,
774, 735, 696; HRMS (HR-APCI) m/z calcd for C19H29O2Si
[M + H]+ 317.1937, found 317.1936.
4.38 | tert-butyldimethyl
(((1S*,1aS*,3aS*,6aS*,6bR*)-1a-methyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (18c)
Colorless liquid, 66% yield; Rf = 0.43 (silica gel, n-Hexane);
1H NMR (400 MHz, CDCl3, 24ꢀC, δ) 5.77 (dd, J = 10.1,
2.3 Hz, 1H), 5.61–5.58 (m, 2H), 5.11–5.07 (m, 1H), 3.26 (d,
J = 7.1 Hz, 1H), 2.96 (d, J = 3.3 Hz, 1H), 2.71–2.56 (m,
3H), 2.02 (d, J = 15.0 Hz, 1H), 1.19 (s, 3H), 0.91 (s, 9H),
0.10 (s, 4H), 0.09 (s, 3H); 13C NMR (75 MHz, CDCl3, 24ꢀC,
δ) 135.6 (CH), 131.4 (CH), 128.0 (CH), 127.4 (CH), 63.6
(CH), 41.0 (CH2), 40.3 (CH), 34.6 (CH), 29.8 (3xCH3), 25.9
(CH), 20.6 (CH3), 18.1 (C), 17.0 (C), −4.9 (CH3), −5.0
(CH3); IR (neat, cm−1) 2,929, 2,827, 2,360, 1,720, 1,462,
1,361, 1,254, 1,106, 837, 779, 679, 417; HRMS (EI) m/z
calcd for C17H28OSi [M]+ 276.1909, found 276.1906.
4.41 | tert-butyldimethyl
(((1R*,1aS*,3aS*,6aS*,6bR*)-1a-vinyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (17d)
Colorless liquid, 50 mg, 27% yield; Rf = 0.35 (silica gel, n-
1
Hexane); H NMR (400 MHz, CDCl3, 24ꢀC, δ) 5.77 (dd,
J = 17.2, 10.7 Hz, 1H), 5.69 (dd, J = 10.3, 1.9 Hz, 1H),
5.63–5.59 (m, 2H), 5.38 (dd, J = 10.2, 2.2 Hz, 1H),
4.91–4.81 (m, 2H), 3.34 (d, J = 6.8 Hz, 1H), 3.16 (t,
J = 5.6 Hz, 1H), 2.78–2.63 (m, 2H), 2.12–2.08 (m, 1H),
1.49 (d, J = 6.9, Hz, 1H), 0.89 (s, 9H), 0.06 (s, 3H), 0.00 (s,
4.39 | (3aR*,4S*,7R*,7aS*,9R*)-9-((tert-
butyldimethylsilyl)oxy)-5-vinyl-3a,4,7,7a-
tetrahydro-1H-4,7-ethanoinden-8-one (S3d)
13
3H); C NMR (75 MHz, CDCl3, 24ꢀC, δ) 142.7 (CH),
White solid, 650 mg, 42% yield; Rf = 0.35 (silica gel,
EtOAc: n-Hexane = 1:15); H NMR (400 MHz, CDCl3,
135.0 (CH), 130.4 (CH), 128.2 (CH), 121.4 (CH), 109.4
(CH2), 65.4 (CH), 41.2 (CH2), 38.3 (CH), 36.8 (CH), 27.2
1

HUNG ET AL.
15
[9] (a) M. Johansson, R. Hjertberg, H. Anke, K. Dekermendjian,
A. Szallasi, E. Thines, R. Witt, O. Sterner, Bioorg. Med. Chem.
1997, 5, 1363. (b) S. K. Thompson, C. H. Heathcock, J. Org.
Chem. 1990, 55, 3004. (c) R. Bergman, T. Hansson, O. Sterner,
B. Wickberg, J. Chem. Soc. Chem. Commun. 1990, 865.
[10] (a) J. Gustafsson, O. Sterner, Tetrahedron 1995, 51, 3865.
(b) M. Johanssona, I. Aujarda, D. Rome, H. Anke, O. Sterner,
Z. Naturforsch. 2005, 60b, 984. (c) D. Rome, E. Arzel,
M. Johansson, O. Sterner, ARKIVOC 2008, 2008, 91.
(d) K. H. Kim, H. J. Noh, S. U. Choi, K. M. Pork, S.-J. Seok,
K. R. Lee, J. Antibiot 2010, 63, 575.
[11] C.-C. Wang, Y.-C. Ku, G. J. Chuang, J. Org. Chem. 2015, 80,
10979.
[12] (a) C.-C. Liao, K. R. Peddinti, Acc. Chem. Res. 2002, 35, 856.
(b) C.-C. Liao, Pure Appl. Chem. 2005, 77, 1221. (c) S. Quideau,
L. Pouysegu, Org. Prep. Proced. Int. 1999, 31, 617.
(CH), 26.3 (C), 25.9 (3xCH3), 18.1 (C), −5.1 (CH3), −5.6
(CH3); IR (neat, cm−1) 3,081, 3,051, 3,015, 2,950, 2,921,
2,894, 2,856, 1,625, 1,475, 1,412, 1,360, 1,340, 1,328, 1,289,
1,250, 1,185, 1,070, 1,031, 997, 971, 951, 939, 891, 859,
778, 723, 700, 616; HRMS (HR-APCI) m/z calcd for
C18H29OSi [M + H]+ 289.1988, found 289.1990.
4.42 | tert-butyldimethyl
(((1S*,1aS*,3aS*,6aS*,6bR*)-1a-vinyl-
1,1a,3a,4,6a,6b-hexahydrocyclopropa[e]
inden-1-yl)oxy)silane (18d)
1
Colorless liquid, 107 mg, 70% yield; H NMR (400 MHz,
CDCl3, 24ꢀC, δ):6.14–6.03 (m, 1H), 5.86 (dd, J = 17.6,
10.8 Hz, 1H), 5.61 (s, 2H), 5.25 (dd, J = 10.4, 2.3 Hz, 1H),
5.18–5.01 (m, 2H), 3.41–3.30 (m, 1H), 3.22 (d, J = 3.8 Hz,
1H), 2.74–2.63 (m, 2H), 2.14–2.01 (m, 1H), 1.50 (d,
J = 2.7 Hz, 1H), 0.93 (s, 9H), 0.11 (d, J = 6.8 Hz, 6H); 13C
NMR (75 MHz, CDCl3, 24ꢀC, δ) 138.4 (CH), 134.8 (CH),
128.2 (2xCH), 126.1 (CH), 111.4 (CH2), 66.1 (CH), 40.8
(CH2), 40.3 (CH), 34.8 (CH), 32.1 (CH), 28.2 (C), 25.8
(3xCH3), 18.1 (C), −4.9 (CH3), −5.1 (CH3); IR (neat,
cm−1) 3,084, 3,052, 3,019, 2,955, 2,928, 2,899, 2,856, 1,627,
1,471, 1,413, 1,361, 1,348, 1,329, 1,289, 1,256, 1,186, 1,071,
1,032, 997, 970, 959, 939, 893, 859, 837, 778, 723, 700, 666;
HRMS (HR-APCI) m/z calcd for C18H29OSi [M + H]+
289.1988, found 289.1993.
[13] Preparation of 3a-c:(a)S. K. Chittimalla, C. Bandi, S. Putturu,
R. Kuppusamy, K. C. Boellaard, D. C.-A. Tan, D. M.-J. Lum,
Eur. J. Org. Chem 2014, 12, 2565. (b) C.-H. Lai, Y.-L. Shen, M.-
N. Wang, N. S. K. Rao, C.-C. Liao, J. Org. Chem. 2002, 67,
6493.
[14] Preparation of 3d, S. K. Chittimalla, C. Bandi, S. Putturu, RSC
Adv. 2015, 5, 8050.
AUTHOR BIOGRAPHIES
Wei-Chun Hung received his Mas-
ter's degree in 2017 from the Chung
Yuan Christian University, working
in the group of Prof. Gary Jing
Chuang. His research interest is light
induced rearrangement reaction and
natural product synthesis. He is cur-
rently working in semiconductor industry.
ACKNOWLEDGMENTS
The authors acknowledge Ministry of Science and Tech-
nology of Taiwan (MOST), Grant/Award Number: MOST
108-2113-M-033-007.
Yung-Ching Chen received his
Master's degree in 2017 from the
Chung Yuan Christian University,
working in the group of Prof. Gary
Jing Chuang. His research interest is
light induced rearrangement reac-
tion. He is currently working in
material industry.
ORCID
Gary J. Chuang https://orcid.org/0000-0001-6058-9185
REFERENCES
[1] R. S. Givens, W. Frederick Oettle, R. L. Coffin, R. G. Carlson,
J. Am. Chem. Soc. 1971, 93, 3957.
[2] M. D. Karkas, J. A. Porco Jr., C. R. J. Stephenson, Chem. Rev.
2016, 116, 9683.
[3] C.-F. Yen, C.-C. Liao, Angew. Chem. Int. Ed. 2002, 41, 4090.
[4] G.-H. Niu, P.-H. Liu, W.-C. Hung, P.-Y. Tseng, G. J. Chuang,
J. Org. Chem. 2019, 84, 10172.
[5] B. D. Schwartz, E. Matousova, R. White, M. G. Banwell,
A. C. Wills, Org. Lett. 2013, 15, 1934.
Guang-Hao Niu received his Ph. D
degree in 2018 from the Chung Yuan
Christian University, working in the
group of Prof. Gary Jing Chuang. His
research interest includes light
[6] V. Singh, S. Q. Alam, Chem. Commun. 1999, 2519.
[7] P. Siengalewicz, J. Mulzer, U. Rinner, Eur. J. Org. Chem. 2011,
2011, 7041.
[8] (a) P. Yates, K. E. Stevens, Tetrahedron 1981, 37, 4401.
(b) M. G. Banwell, G. J. Harfoot, Aust. J. Chem. 2004, 57, 895.
(c) D.-S. Hsu, Y.-Y. Chou, Y.-S. Tung, C.-C. Liao, Chem. Eur. J.
2010, 16, 3121.
induced rearrangement reaction, nat-
ural product synthesis and ligand
design for transition metal complex. During his gradu-
ate course he visited Barnard College, NY as an
exchange student under the guidance of Prof. Michael
G. Campbell. He is currently working at National

16
HUNG ET AL.
SUPPORTING INFORMATION
Health Research Institutes of Taiwan as a postdoc-
toral fellow, working with Dr. Jinq-Chyi Lee.
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
Gary Jing Chuang obtained the
Ph.D. degree in 2007 from the
National Tsing Hua University under
the guidance of Prof. Chun-Chen
Liao. He has joined Chung Yuan
Christian University since 2011 and
How to cite this article: Hung W-C, Chen Y-C,
Niu G-H, Chuang GJ. Studies on photochemical
rearrangement of non-oxygenated bicyclo[2.2.2]
octenones and mono-oxygenated bicyclo[2.2.2]
octenones from masked o-benzoquinones: Access
to protoilludane and marasmane skeletons. J Chin
Chem Soc. 2020;1–16. https://doi.org/10.1002/jccs.
201900460
is currently an associate professor in
the department of chemistry. Previously he has
worked as a postdoctoral fellow at Harvard University
in the research group of Prof. Tobias Ritter. His
research interests include light induced rearrangement
reaction, bimetallic catalysis and natural product
synthesis.